Various passive occupant restraint belt systems have been proposed in which a seat belt is arranged to move automatically from an occupant restraining position to an occupant releasing position. While such systems generally employ means for shifting the belt away from the body of the vehicle occupant, and hence permit the occupant to enter and leave the vehicle, the particular means so employed vary widely. For example, electrical sensing devices and motors may accomplish the desired shifting function but only at relatively great expense.
Other systems, such as disclosed in co-pending U.S. patent application Ser. No. 195,726 filed Oct. 10, 1980, which corresponds to Japanese Utility Model Registration Application 54-143328 filed Oct. 18, 1979, employ mechanical linkages which, in response to the opening and closing of the vehicle door, cause the seat belt to move from a restraining to a non-restraining position. The present invention is of this type.
In passive restraint belt systems which move in response to the opening and closing of the vehicle door, it has also been proposed to provide for full movement of the system even though the vehicle door may be opened only partially. This is because there are often encountered situations, such as on narrow roadways or in tight parking spaces, where the occupant is unable to fully open the vehicle in order to enter or leave the vehicle. In such systems, however, relatively complicated, costly or fragile mechanisms have heretofore been employed.
The relative complexity of systems which are fully responsive to only partial door movement is caused primarily by the fact that lost-motion couplings must be included for permitting the door to move from a partially open to fully open position without further affecting the movement or operation of the seat belt system. Moreover, since the mechanical linkages for detecting and responding to door movement are commonly located at the lower portion of the hinged (i.e. front) edge of the vehicle door, various motion amplifiers have been required in order to obtain the desired seat belt movement in response to the relatively small displacement of the front door edge as the door is partially opened.
The present invention is, therefore, directed to a passive seat belt system which includes these features and which is at the same time relatively simple, inexpensive, and dependable.